Answer: In rare head injury cases resulting in acquired savant syndrome, a person may suddenly gain intelligence in a specific set of skills.
From http://www.techeblog.com/index.php/tech-gadget/man-suffers-severe-concussion-becomes-musical-genius
It is very difficult to measure or quantify “smart,” since there are many different scales by which one can measure intelligence. In rare cases of head injury, genius-like talents can appear spontaneously. This has come to be known as “acquired savant syndrome.”
Derek Amato. After a severe concussion, Amato became amazingly talented at playing the piano, despite never having played before the accident.
Alonzo Clemons. He sustained a severe head injury as a child after falling. Although he exhibits some cognitive deficits, he gained the ability to sculpt remarkably accurate models of animals.
Tony Cicoria. Dr. Cicoria, an orthopedic physician, was struck by lightning from a telephone. He, like Amato, became obsessed with playing piano. Months after his injury, he became a composer and has performed at several venues.
Orlando Serrell. Developed the inexplicable talent of being able to name the day of the week for any given date after being struck in the head by a baseball. He could also recall the events of that day and to some extent, the weather.